Umbra on mulch

Spring is upon us and the season for spreading shredded bits of trees around our landscaping is here. How does Umbra feel about the utility of mulching, and what is the environmental impact of mulch production?

OmarEllicott City, Md.

Dearest Omar,

Umbra feels excited about spring, I’ll tell you that much. Umbra is jumping up and down with glee, sometimes on top of slugs. Umbra is very pro-mulch, and very happy to choose mulch questions over diaper questions. (Don’t worry about it, parents!)

Mulch — pile it on!

Photo: NRCS.

Mulching is piling any type of organic material in the garden in order to suppress weeds, improve the soil, and/or make an aesthetic statement. You can mulch with wood chips, compost, bark, newspaper, straw, recently weeded plants, all sorts of handy matter. (Note, however, that mulches do vary in their nutritive properties.)

Now, a vocabulary lesson. Tilth is a word that refers to the health of the soil, and healthy soil is full of bugs, fungus, bacteria, air space, and humus. Humus is organic matter stabilized within the soil matrix. Mulching is a reliable way to improve both humus and tilth, particularly because it is no-till — that is, it adds to the soil by layering, not by digging, and does not disturb whatever is already happening down below. And mulching also improves water-holding capacity. Healthy soil requires less irrigation and acts as a sponge for surface runoff; in other words, it will use less freshwater and absorb more would-be wastewater. Mulching is therefore excellent for your microenvironment.

Your question about the environmental impact of mulch production is a bit confusing to me, but maybe you are buying mulch in bags and are concerned about the provenance of the contents. However, you needn’t fear: it’s easy to find mulch made of waste products from other industries, so you will be reusing and recycling by mulching. To find your local sources for bulk and bagged mulch, get in touch with your local gardening volunteers and experts, the Master Gardeners. You’ll find them on the web by searching for Master Gardener + your state or county. (Omar, I believe yours are the Howard County Master Gardeners.) They should have local mulch resources for you, which can help you distinguish the source of your mulch to your satisfaction. Where I live, for example, I can mulch with composted yard waste, or with chipped trees from local arborists. Mulch ho, my friend.